Control valves are commonly used in process plants to control the flow of a fluid (e.g., a gas, a liquid, etc.) or any other substance through pipes and/or vessels to which they are connected. A control valve is typically composed of one or more inlets and outlets, and includes a flow control element or member (e.g., a valve gate, a piston, a valve plug, a closure member, etc.) that operates to control fluid flow through apertures that fluidly couple the inlet(s) to the outlet(s). A closure member is typically coupled to a valve bonnet that is mechanically coupled (e.g., bolted, clamped, threaded into, etc.) to the valve body. Typically, the closure member is configured to engage a sealing structure (e.g., a seat ring) that encompasses a flow path through the valve.
In some instances, different components of the control valve are made of different materials having different coefficients of thermal expansion. As such, in high temperature applications, the coefficients of thermal expansion of the materials from which the different control valve components are made have to be taken into account.